Strontium ions capturing in aqueous media using exfoliated titanium aluminum carbide (Ti2AlC MAX phase)

Abstract The etching of MAX phases using hydrofluoric acid (HF) is not environmentally-friendly. Therefore, in this study, a MAX phase named Ti2AlC was synthesized and etched using a green hydrothermal alkalization approach, resulting in nanofibers (Alk–Ti2Cfibr) and sheet-like (Alk–Ti2Csheet) nanostructures. Nanostructures with exceptional physicochemical properties with an excessive number of active binding moieties were deployed to remove radioactive strontium ions (Sr2+) from matrices, such as deionized (DI), tape, and seawater. The synthesized nanostructures were characterized using analytical techniques, including X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. The synthesized nanostructures were highly stable in water, unlike other HF-etched MXenes, possess a unique structure, large surface area, and are enriched with oxygenated terminal groups. Sr2+ adsorption performance of nanofibers and nanosheets was evaluated in typical batch tests. The nanostructure unveiled a maximum adsorption capacity of 296.46 mg/g, which is among the maximum removal capacity reported for similar removal, including identical graphene oxide and its composites. Additionally, in seawater, Sr2+ adsorption capacity was 3543.33 µg/g with more than 95% removal efficiency. The adsorption mechanism study confirms the electrostatic interactions between Alk–Ti2Csheet and Sr2+.